Prince Philip investigated UFOs for 70 years.
Alien buffs have called for ministers to make the late Duke of Edinburgh's findings public following the death of his wife Queen Elizabeth.
Prince Philip, who died aged 99 in 2021, developed a "fascination" for little green men after a close encounter at the home of his uncle Lord Louis Mountbatten in 1955.
It has been claimed that the late royal spent much of his life investigating extraterrestrials but the matter was kept quiet as it would have "caused a sensation".
Former Ministry of Defence official Nick Pope, who manned the UK Government's UFO research during the 1990s, claimed that Philip "kept an eye on developments, subscribed to UFO magazines and newsletters and had witnesses interviewed".
Pope told the Daily Star newspaper: "This is highly sensitive.
"Here you have the Queen's husband investigating UFOs. Had the news got out it would have caused a sensation."
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